I've developed a site which I now want to rename before launching it...Can I just rename the folder, or do I need to rename the cache also or is there a best way so I don't Eff everything up like linked css etc??

As far as I know, you can just rename the site and it will update the cache. However, it really doesnt matter. You could have your site named "myFirstSite" and still upload it to your server. The only thing that matters is that you have your "Remote Info" set correctly. You'll notice that when you click on "remote info" and choose "FTP" all you have to do is set the info. There is nothing that has to do with the site name on your computer.

"The greatest thing the devil ever did was convince you he didn't exist." =- The Usual Suspects